1. Field of the Invention
This invention relates to a finisher, which is connected to an image forming apparatus such as a printer or a copying machine, giving such additional-workings as sorting, binding, creasing, folding, and punching to a recording medium (hereinafter referred to briefly as "sheet") such as a recording paper outputted from the image forming apparatus. More particularly, it relates to a finisher with a folding device in which a stopper comes in contact with the leading end of the sheet to form a loop and a pair of rollers nips the loop to fold the sheet.
2. Description of the Related Art
Recently, various finishers, which give various additional-workings to a sheet with an image formed surface which are outputted from such image forming devices as printers and copying machines, have been proposed (U.S. patent application Ser. No. 08/821,444). The term "additional-workings" as used herein means various working processes such as sorting sheets according to the number of copies, filing sheets with staples, folding sheets in two (hereinafter referred to as "double-folding"), folding sheets in three or in a cross section like a letter Z (hereinafter referred to as "Z-folding"), and punching sheets for filing.
A finisher, which is illustrated in FIG. 19, has been known as one example of the above finishers. The finisher is provided with a folding mechanism 700. The finisher gives the Z-folding to sheets as follows. First, the folding mechanism 700 receives a sheet with a copied image on the upper surface, which is fed from the direction of right in the diagram. A first folding stopper 704 comes in contact with the sheet to form a loop of the sheet. Then, a pair of folding rollers 701, 702 nips the loop to effect the first folding at a position separated by about one quarter of the size of the sheet in the conveying direction from the leading end of the sheet. Next, the second folding stopper 705 comes in contact with the first folding to form a loop of the sheet. Last, a pair of folding rollers 702, 703 nips the loop to effect the second folding at a roughly central position of the sheet in the conveying direction. Accordingly, the sheet is in three or in a cross section like a letter Z.
The above conventional folding devices adopt a so-called last page system which copies a plurality of original documents sequentially in the reverse order from the last page forward. The last page system, which is provided with the folding mechanism 700 disposed below the finisher as illustrated in the diagram, can change the sheets to be in the order of page numbers.
Incidentally, multifunction machines, which work as a printer, facsimile equipment and the like, have been proposed with the popularization of digital copying machines. Such a multifunction machine is utilized for various purposes of copying, printing, facsimile receiving, facsimile transmitting, etc. A user is possibly confused on the occasion of a series of printing when all functions do not have the same printing order as the order from the first page onward or in the reverse order from the last page forward.
The application programs, which are executed by a computer, normally give a printer instructions of printing in the order from page 1 onward. Accordingly, a large number of multifunction machines adopt a so-called first page system in which a printing starts from the first page onward as the common printing order applied to all functions.
The first page system, however, requires to discharge a sheet having a copied image in a reversed state for adjusting the order of page numbers. A folding device according to the conventional folding device illustrated in FIG. 19, providing with a reversing mechanism 710a on the front of the folding mechanism 700 as illustrated in FIG. 20 (on condition that a reversing mechanism 710b is not incorporated), folds a sheet concerning a surface opposite from an image formed surface C as illustrated in FIG. 21 and does not obtain a proper folding when discharging a sheet having a copied image in a reversed state. A folding device according to the conventional folding device illustrated in FIG. 19, providing with a reversing mechanism 710b on the front of the discharging unit as illustrated in FIG. 20 (on condition that a reversing mechanism 710a is not incorporated), folds a sheet concerning the image formed surface C. However, the folding device has to staple a sheaf of temporarily stored sheets as illustrated in FIG. 22, at a stapling position S as the farthest position in a conveying direction of the sheaf when the folding device takes the sheaf out in a direction opposite to a receiving direction of the sheets for temporarily storage. Namely, the folding device has the problem that the stapling is difficult.
In the first page system, it is preferable to store sheets in such a manner as illustrated in FIG. 23 for the purpose of fixing the stapling position S in the conveying direction for all the sizes of sheets. It results in shortening the conveying distance of sheets or a sheaf necessary for stapling on the downstream side, securing the accuracy of positioning steadily and reducing the deviation of sheets during the conveyance, for example.
An arrangement as illustrated in FIG. 24, which reverses a sheet P, irrespectively of the necessity for a folding, may store sheets in such a manner as illustrated in FIG. 23.
In the arrangement, the conveying path is not easily laid out unless the folding mechanism 700 is disposed above the finisher. In generally, a finisher stores sheets P temporarily, staples a sheaf of stored sheets and discharges a stapled sheaf into another receiving tray unit. A position of the receiving tray unit which stores a stapled sheaf is preferably lower than a position of the stapler for stapling a sheaf for the purpose of attaining the conveyance of the sheaf steadily. A tray, which temporarily receives sheets, must be inevitably disposed on the upper section for the purpose of enlarging a storage capacity for stapled sheaves. A finisher including the folding mechanism 700 disposed on the upper section as well as the tray is of large size as a whole, and loses balance because a component density is high in the upper section.